In the last few years there has been much research aimed at trying to determine the colours of both ancient birds and non-avian dinosaurs. Examination of the microstructure of fossil feathers under powerful electron microscopes can reveal the shape of colour-forming "packages" called melanosomes. Since the shape of a melanosome is strongly linked to the colour it produces, this relatively simple observation can actually reveal some of the colours and patterns of animals from tens of millions of years in the past. Exciting and important though this work is, melanosome shape tells only part of the story, and still more technologically advanced techniques are being brought to bear on the problem.

Palaeontologists have always tried to maximise the amount of data that they can extract from fossils as they are rare and tend to be incomplete. While electron microscopes allow us to look at things as tiny as a few nanometres across (that's a billionth of a metre, or a millionth of a millimetre), researchers have recently been trying to look at the underlying chemistry of the fossil feathers as well.

Using the synchrotron particle accelerator, traces of various elements in the fossils can be detected and mapped. This has potentially huge implications because while the feathers or similar soft tissues may decay, key chemical traces (like copper, which is often part of a red colour in feathers) may remain and can be detected. In short, even if there is no apparent trace of a feather, or maybe even a melanosome, traces that can be linked to the original colours might remain.

A recent synchrotron analysis of the chemical traces of the fossil feathers from the famous "first bird" Archaeopteryx suggests that the leading edge and the tip of wing feathers in this animal were generally darker, while the trailing edges had little pigmentation and could well have been white.

Part of the ‘Thermopolis’ specimen of
Archaeopteryx under UV light. Image courtesy of Helmut Tischlinger. Helmut Tischlinger

In the case of the Archaeopteryx trace elements, whole fossils have been scanned, but other techniques do require the removal of tiny samples of the feathers or other tissues for analysis. However, actually finding a sample in the first place can also be an issue in itself.

While some fossil feathers show up as very clear, dark patches on the fossils, others are rather more elusive. Indeed, entire bones can be hard to see when they are a near identical colour to the rocks that entomb them. Humans, though, have a rather limited range of vision under natural lighting, limiting what we can perceive. So moving away from what we would consider a normal spectrum and into the UV range can dramatically alter the appearance of fossils revealing new details, and, on occasion, reveal something that's frankly beautiful.

Scientists have been looking at fossils under UV for over a century, but it's only in recent years with more powerful and commercially available lamps that this has taken off. Even so, it remains a frustratingly overlooked medium as, not only are the results often visually stunning, the technique has helped to reveal quite a number of important but otherwise hidden features that had been invisible before. Pieces of skin and feathers, patterns of scales, beaks and claws, whole display crests and even arm and leg muscles have been found through UV work. The synchrotron may reveal depths and details in fossil never previously seen, but it really helps to have some companion technique that can help detect the fossils most likely to reveal the kind of fine details you are after.

Scientists do get criticised for taking reductionist approaches and analysing with the head and not the heart (though people who do this seem to be missing the point of science) but images like these are, to me at least, every bit as wonderfully aesthetic as they are palaeontologically illuminating. Beauty in this case, is skin (or feather, or muscle) deep.